The Rel/NFkB familiy of transcription factors is widely expressed and influences the expression of numerous genes, including many involved in immune and inflammatory responses. Understanding the regulation of this family is therefore an important step toward influencing these responses. We are studying the activity of NFkB, and of its inhibitor IkB, in persistently activated cells. We are also interested in the role of NFkB in apoptosis and have collaborated with Dr. Karen Vousden in demonstrating that this role differs depending on the status of cellular p53. In addition, we are focusing on the role of NFkB in the differentiation of normal peripheral blood monocytes into cells possessing many of the phenotypic and functional properties of dendritic cells (DC). DCs are the most efficient of the body's antigen-presenting cells and hence are critical for proper immune system function. They are of special interest currently because of their possible therapeutic utility. To facilitate the study of signaling pathways involved in DC differentiation, we developed a serum-free culture system in which monocytes differentiate rapidly (48-96 hours) in response to bacterial lipopolysaccharide, tumor necrosis factor, or calcium ionophore. In spite of significant differences in the signaling pathways utilized by these agents, they all activated members of the NFkB family, including RelB. Furthermore, agents which prevented NFkB activation also blocked DC differentiation, suggesting that NFkB is required for the differentiation process. We are currently performing RNase protection assays and gene array experiments in order to analyze the pattern of gene activation during differentiation.
